libansilove: update to 1.1.6.

ChangeLog:

libansilove 1.1.6 (2019-11-18)

- Use CMAKE_INSTALL_{LIB,INCLUDE}DIR instead of hardcoding directories
- Introduce a XBIN_PALETTE_LENGTH macro
- Use XBIN_HEADER_LENGTH and XBIN_PALETTE_LENGTH macros instead of magic
  numbers
- Add another format validation check (palette size) in the XBin loader

(fcambus)